This article is from the Coffee and Caffeine FAQ, by Alex Lopez-Ortiz with numerous contributions by others.
It is very important that you wash your coffee maker pot and filter
container thoroughly at least once a week. Bitter oils stick to the
glass container and plastic filter holder.
I used to wash the plastic filter container and rinse the glass pot.
Coffee started to taste bad. When I was told to wash both thoroughly
with plenty of soap the flavour improved instantly. Note: To the naked
eye rinsed and soap washed pots look the same (clean that is).
Some drip coffee makers require periodic cleansing with a solution of
water and vinegar.
If you have a coffee/teapot, the inside of which is stained with oily
brown residues - also plastic/metal coffee filters, tea strainers, and
stainless steel sinks in caffeine-o-phile houses - they can be
restored to a shining, brand-spanking-new state by washing in hot
washing powder (detergent).
Get a large plastic jug, add 2..3 heaped tablespoons of Daz Automatic
or Bold or whatever, and about a pint of hot water - just off the boil
is the best.
Swill the jug around until the detergent is dissolved, and then pour
into tea/coffeepot, and let it stand for 5 minutes, swilling the pot
around occasionally, just to keep the detergent moving. Put the lid on
and shake it a few times (care: slippery + hot)
Repeat as necessary. Keep it hot with a little boiling water if
needed. If you have a cafetiere, dissemble it, and soak the parts in
the mixture for a few minutes, agitating occasionally.
In both cases, the residue just falls off with almost no scrubbing. It
does great things with over-used filter machine filters, too.
Important: Rinse off all detergent afterwards, use lots of fresh
water.
 
Continue to: